Row Objects

Row Objects
calac41
Row objects are key objects in API and logic processing. When you create an API and connect API Creator to your database,
CA Live API Creator
 builds a JavaScript object model and creates a row object type for each base table. You can think of these as Object-Relational Mapping (ORM) objects: the object model provides access to attributes and related objects, read/write persistence services, and logic enforcement. Objects refer to the JavaScript objects created as part of the JavaScript object model. For example, the Demo API includes the 
customer
 and 
purchaseorder
 objects.
CA Live API Creator
 updates this model automatically (for example, if you change the schema) when you reload your schema.
The row object type provides familiar persistence and accessor functions. 
In this article:
2
In most applications, you shape your API by explicitly defining resources in your API. These resources provide multi-object retrieval and update.
For more information about how to shape your API, see Customize your API.
The following diagram shows an API PUT/POST request containing a JSON document (the leftmost object) that consists of an Order and possibly several Items:
resource row logic.png
Persistence
The row object type provides persistence. Like ORM objects, these row-object types are persistence-enabled. You can access attributes and related data using these row objects. You can handle the update events that these row-object types expose in JavaScript.
As ORM objects,
CA Live API Creator
 reads and writes rows to disk. The read/write occurs in the following ways:
  • CA Live API Creator
     saves submitted rows
    READ, INSERT, UPDATE, and DELETE verbs and save changed rows, with logic enforcement.
  • CA Live API Creator
     saves chained updates
    Your logic can cause 
    CA Live API Creator
    to retrieve and update related rows. For example, the previous diagram shows that 
    CA Live API Creator
    submitted Order and Item. It also shows that logic caused an adjustment of a Customer, which 
    CA Live API Creator
    saves.
     
    CA Live API Creator
    brackets requests into a transaction.
  • CA Live API Creator
     does the following:
    1. Submits rows to your logic, for example, in logic event rules.
      For more information about logic event rules, see Event Rule Types.
    2. Passes these rules the
      l
      ogicContext
      object, which provides APIs for reading data in 
      CA Live API Creator
      and altering it.
      For more information about the 
      logicContext
       object, including persistence, see The logicContext Object.
    3. Saves submitted/changed updates to rows to disk at the end of the transaction.
Resource/Row Mapping
The row object type provides resource/row mapping. You make update requests by way of resources that you explicitly define in your API. 
CA Live API Creator
shares the row logic over all these resources by mapping (transforming) them to rows.
Request Event Processing
CA Live API Creator
 processes request events using the following workflow:
  1. CA Live API Creator
     invokes your request event handler, providing you an opportunity to reformat the JSON. For example, you can reformat the JSON or, for complex transaction-handling, you can inject 
    @metadata
     tags.
  2. CA Live API Creator
     creates table rows from each JSON row.
  3. One of the following occurs:
    • (PUT operations) 
      CA Live API Creator
      retrieves the values that are not included in the JSON row (so the ensuing logic always sees a "full" row) and performs optimistic locking checks.
    • (POST operations, or rows that are designated with the insert 
      @metadata
       action tag) 
      CA Live API Creator
       generates the primary key (for example,
      OrderId
      ) by inserting the row into the database.The value is cascaded into the foreign keys of contained rows (for example,
      OrderId
      is placed into each Item).
For more information:
Logic Execution
The row object type provides logic execution. Rows are rich, not anemic, domain objects. They provide access to attributes and persistence and enforce your business logic. When the client makes PUT/POST/DELETE requests, they invoke the relevant reactive logic and events you have defined.
For more information:
Logic Phase Processing
For each row, 
CA Live API Creator
invokes your reactive logic automatically based on what changed in a row. Reactive logic can chain to update other related rows, for example, the Order can adjust the customer's balance. Logic invocation and ordering are system-defined, which reduces errors and simplifies maintenance.
For more information about reactive logic, see Logic.
Commit Phase Processing
After all the rows are processed, and all the derivations have been done, 
CA Live API Creator
executes commit validations and events. In this way you can specify logic such as "an order must have one or more items", for example:
Derive Order.itemCount as count(items)
Commit Validation - Order.itemCount > 0
Logic Coding
Typically you specify your logic in server-side JavaScript. 
CA Live API Creator
 passes key information required for its operation to you logic:
  • row
    ,
    oldRow
    . The rows that were submitted or chained.
  • The
    l
    ogicContext
     object, which provides services to read/write other rows.
Your logic can read/write the row attributes and access related data.
For more information about server-side JavaScript events, including logic event rule types, see Quick Reference.
Attribute/Related Object Access
The row object type provides attribute/related object access. Rows are passed to your logic and events and provide access to attributes (
row.OrderDate
) and related objects (
row.Customer.name
).
Row objects have the following behaviors:
  • Attributes.
     Rows have attributes for every column. For example, you can refer to an order's 
    amount_total
     using
    row.amount_total
    .
  • Parent role accessors. 
    Rows provide accessors to parent data, for example:
    var department = 
    row.headDepartment
    ;     // head department for current department row
    var deptName = row.headDepartment.name;  // or, data in the row
  • Child role accessors.
     Rows provide role accessors. You can refer to an orders' 
    row.customer.balance
     or obtain a collection of 
    row.lineitems
     (a collection of line item rows).
    var worksForEmps = 
    row.reportingEmployees;
      // child role name
          for (var eachEmpNo in worksForEmps) {
            var eachEmp = worksForEmps[eachEmpNo];
            logicContext.logDebug(eachEmp);
        }
    You can get code completion access to row attributes and role accessors using the JavaScript code editor in API Creator.
    For more information:
    For more information:
    There can be many child rows (more than a few thousands). Be careful about iterating over them using this method. This method can use up a significant amount of memory and CPU.
Show Attribute Values for Logging and Debugging
You can show attribute values for logging and debugging using the 
toString()
method.
 For more information about logging and debugging, see Debug.
Metadata Access
CA Live API Creator
 passes the
logicContext
object to your rules and events. The
logicContext
object provides methods to return the description of the row, useful for extension services seeking to deal with rows generically.
For more information about the 
logicContext
 object, see The logicContext Object.